The HP 49G has a step-by-step solve feature so students can see how to arrive at the correct answer.

The HP 49G graphing calculator was developed for advanced math,
science and engineering high school and college students. Users
can choose between algebraic notation or Reverse Polish Notation
(RPN) for entering equations (RPN is a system for representing mathematical
expressions without the use of parentheses). Step-by-step solve
allows students to see the process of obtaining the correct answer.
The HP 49G creates an environment where students can fully integrate
graphic, numeric and step-by-step symbolic manipulations.

With 1.75MB of memory (three times the memory of other calculators
on the market at the time), it cost $180 when it was introduced.
The HP 49G is still sold today.